


SOULECTIVE

by theliatris



Category: Produce 101 (TV)
Genre: Alternate Universe - Detectives, Alternate Universe - Soulmates, Crime Scenes, Crimes & Criminals, Enemies to Lovers, Graphic Description, I Wrote This Instead of Sleeping, Inspired by Jake and Amy's dynamic from Brooklyn 99 (TV Show), Jinhyuk is lowkey Jake but not Jake, Lee Sejin is competitive, Lowkey B99 AU??, M/M, Murder Mystery, Partners to Lovers, Soulmate-Identifying Marks, Soulmate-Identifying Timers
Language: English
Status: Completed
Published: 2020-04-01
Updated: 2020-04-01
Packaged: 2021-02-28 20:15:20
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 7,270
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23423029
Author URL: https://archiveofourown.org/users/theliatris/pseuds/theliatris
Summary: Sejin never tells anyone ever about the birthmark he has on his left forearm until Jinhyuk, a new detective, came to his life and something changed with his birthmark.
Relationships: Cho Seungyeon | Seungyoun/Kim Wooseok | Wooshin, Lee Jinhyuk/Lee Sejin (Produce 101)
Kudos: 12





	SOULECTIVE

**Author's Note:**

  * For [dreverizzle (Dilia)](https://archiveofourown.org/users/Dilia/gifts).



> Trigger warning: detailed crime scene ⚠️, mention of death and murder (you can scroll past the ⚠️ sign if you still wish to read for the story without crime-related plot).

“ _Someone is found dead again_.” Byungchan dropped the news as soon as he opened his apartment’s door for Sejin, who now had to look up and adjusted his beige beret in a rather surprised expression. It’s not that Sejin didn’t expect this news, but to hear a new murder case in less than two days? This district hadn’t had a big case like this in the last two months. This surely raised another possibility of Sejin’s previous deduction. Sejin creased his eyebrows and slid in sideways –Byungchan never let his door open too wide—, Sejin bit his tuna sandwich that’s been hanging between his mouth and crashed himself in the nearest couch, putting down his backpack.

⚠️

“They got their private part cut again this time.” Byungchan continued after he shut his door tight, following Sejin in, and Sejin choked.  
⚠️

“Hold on.” Sejin grabbed his water bottle from his bag's side and gulped it down. He bit the rest of his sandwich quickly, held one hand up for Byungchan to wait. There is no such thing as losing appetite when you are in this field of work, running around in an empty stomach is not something Sejin would recommend. The desperation of hunger might make one work harder and quicker, yes, but it could also shift his attention to something else than his focus point. It would raise his anger level and decrease his tolerance level, and nothing good would come out of that.

“Now, tell me,” Sejin said at last. Byungchan rolled his eyes and handed him a phone tablet. Sitting on the other single couch in front of his friend who is also his coworker.

“It’s a middle-aged man again, both victims got attacked on their way home from after-work drink session. The culprit didn’t take any valuable belongings for their cards, phones, and expensive watches remained intact. They came from different offices though.”

Sejin listened attentively while he scrolled through the case’s files, several photos of the murder scene and pieces of evidence that were gathered by Seungyoun and Wooseok an hour ago, immediately after a traffic police car who did patrol reported it to the precinct. It took roughly one-hour driving by car from Sejin’s parents’ house to Byungchan’s apartment area, causing Sejin unable to check his phone earlier. 

“Now this sounds a lot more complexed than single case motivated by a jealous ex-wife...” Sejin talked without lifting his head up. “I had a few more leads in my head actually, though I would hate to assume before we hold a meeting tomorrow and create a team for this case if necessary... which I sure hope so. Unless captain would think it’s enough for me and the Busan 96’s couple to work as three.” Sejin ended his commentary in a half sarcastic half playful tone, he rested his back on the couch and unzipped his backpack, pulling up his notebook. Byungchan sympathized, he understood Sejin’s reason, he was about to pat Sejin’s arm to offer emotional support until he remembered, Sejin hates skinship. He retrieved his hand back.

“I heard from Wooseok that we are going to have a new detective officer tomorrow, by the way. Seungwoo personally chose him when there was an offer by the authority to get more heads in our precinct. Perhaps he would be considered to join your team?” Byungchan tried to drop a piece of good news amidst the chaos that’s seemingly happening in their district recently.

It sure got Sejin’s attention, “You sure you heard it from Wooseok, not a captain casually telling what he had just done for the day to his secretary?” He leaned forward.

“Dude, we are not in that kind of relationship.”

“Yeah? I didn’t even mention any kind of relationship, let alone _that_ kind of relationship. Whatever that is.” Sejin’s lips twitched into a smug smile, satisfied with being able to tease his friend in teenager days, way before he joined an academy.

“Sej. What you believe may come true under the theory of manifestation, and believe me, if you don’t stop teasing me and someday we end up happening, you will regret it being surrounded by more couples around you.” 

Sejin’s eyes widened. 

“You have soulmate marks like Wooseok and Seungyoun? Is it a countdown like them?”

“Not really, but who knows? I don’t have any birthmark and I don’t see anything weird above anyone’s head either so far, including _the captain_.” Byungchan emphasized his last two words to let himself go from Sejin’s teasing, “I may be a person who doesn’t have one true love like some lucky people, but it may also appear later in a different kind of sign. I just don’t want the idea to limit me from anything...” 

Sejin nodded, he understood. This whole soulmate business is quite hard to grasp as one kind of general solution and definition since it’s not a universal concept that applies to everyone. Take it from Byungchan’s example, his brother was too stubborn to let go of his supposed to be soulmate he abandoned his family, even after the girl refused his profession of love. Meanwhile, Sejin’s parents were not a soulmate pairing, but their marriage is a happy one, his grandmother on another hand? Had a soulmate she couldn’t marry. Sejin had to understand the concept from many years ago through his grandmother’s tale.

“You are staying for the night, right?” Byungchan now had stood up, facing the direction towards his kitchen. “I will heat some leftover pizza I just ordered one hour earlier before you come, or do you want to order a new one?”

“Nah, I’ll just eat the pizza you will heat. I will look at this case’s details some more, to find the similarity and difference between the two cases.” Sejin raised Byungchan’s phone tablet and his notebook, he has rested his legs on the couch now, putting down his backpack below after covering half part of his body with a thin blanket made of faux fur.

“Okay, wait here.” Byungchan disappeared after taking a turn left from a wall that’s separating his apartment’s living room to his kitchen.

Sejin scribbled some notes on his book. Something he found about from Wooseok’s quick report was that while in the first case the perpetrator didn’t bother to cover the victim’s wound, for this recent case, they actually pulled up the victim’s pants up albeit done in a rush, judging by how the belt wasn’t fastened properly. He was still considering whether this was done by the same person or someone did a copy cat type of crime, although the details of this case were never released to the media people knew someone was dead –killed— by losing a certain part of their body. 

Sejin’s phone and Byungchan’s work phone held by Sejin buzzed at the same time. A new message has just arrived from Seungyoun telling their temporary group of this case –consists of Byungchan, Wooseok, and Sejin— that the autopsy result stated both cases seem to be done with the same weapon, though the wound had a different angle of cutting. There were also three sleeping pills found inside this recent case victim’s stomach. Sejin’s eyebrows furrowed up.

“You need to eat first, man. A tuna sandwich isn’t enough for your brain to crack this case.” Byungchan’s voice cut his train of thought. He appeared through the same door he went from earlier, holding a tray of the plate and a ceramic blue teapot with two cups of the same color, a water bottle hanging from his left hand.

“This might be more serious than what I was deducting at first.” Sejin pulled his knees up, letting Byungchan sit right in front of him –on the same light brown couch—rather than the single one that’s too far on the other side of the table.

Byungchan didn’t immediately answer, there was a silent temporary pause, allowing Sejin to hand over the work-only phone to its rightful owner, before taking a slice of pineapple pizza from the plate Byungchan just put down less than a minute ago.

“This _is_ serious.” Byungchan may not be a detective, his position is a secretary of the captain, but he knows his colleagues too well and witnessed too many cases around the precinct not to be able to know when shit is real.

Sejin likes sleeping over at Byungchan’s place when there is an ongoing case that shows a pattern of being a little too heavier than the rest. Like the possibility of this becoming a serial murder crime concerned both of them, which they were sure Seungyoun and Wooseok thought the same way.

“You know what... I have been thinking.” Byungchan bit the first slice he took, Sejin took the time to wait while sipping from a cup of hibiscus tea which Byungchan had just brought earlier. Smoke was still fading out from the mouth of its teapot next to their saucers.

“This guy which Seungwoo chose, he may be really good.” Byungchan took a quick gulp from his water bottle and –he always prepared all they need at once, he was reliable that way--, and made sure he had swallowed all of his pizza’s piece. “I’m starting to think that Seungwoo noticed it from two days ago when the first murder occurred, that this would lead to something bigger than a single murder, so when he had a discussion, meeting with the authority... he proposed for more heads, more brains.. and he chose the best guy from another department.”

Sejin was processing the information and lowkey wondering why Byungchan just didn’t follow this path of being detective too. At least for passion reason, he seemed to enjoy deduction a lot, and would always welcome Sejin when he needed a friend to discuss. Sejin has a certain rule to never talk about work in his house, although his father was a detective too before meeting his mother, and how he inherited some serious and ambitious side from him, but the both of them had a silent pact to never talk about worrying pieces of stuff, heavy criminal kinds of stuff, over the dinner table or in front of their wife-mother at all.

“Have you met this guy whom Seungwoo chose?” Sejin was reminiscing to a day where a senior sergeant also recommended him to the previous captain before Seungwoo. Not everyone who graduated from his academy got recommended immediately to a field or precinct.

“Lucky me, I met him once.”

Sejin side-eyed Byungchan and about to tease him for his close relationship with their captain until he remembered it would only lead them to a sensitive discussion about soulmate stuff again. Sejin took another bite of his slice, savoring his pineapple to control his mouth from throwing out a playful remark.

“It was just yesterday, actually. When I delivered some documents from Capt to the headquarters, I saw this to-be-new-guy coming out of the office and he bowed to me politely. I know how he looks like because I had to sort his document before getting stamped by the captain, by the way. I heard from my colleague in another department who used to work with him, he was the best student in his year.”

Sejin let Byungchan continued, Byungchan and his connections... with his way of telling, this would take a while. On another note, if this guy was indeed above capable standard, it would help their team at least. Though there was some unusual vibe Sejin felt which he didn’t like about where was this going.

“He worked in precinct 99 previously, before getting promoted to work in the HQ, and now he accepted a challenge to be back helping in precinct Busan 96. Helping, they said... can you believe?”

Sejin was sure he didn’t like how that sound at all. This implied that precinct 96 didn’t do so well they need another help. Though he knew Seungwoo and HQ didn’t really think of it that way. Wooseok and Seungyoun were good detectives and Sejin who currently got the most arrest both in teamwork or when he was assigned only with Wooseok or Seungyoun, or even some old detective that barely did the thinking and only reliable for paperwork for the most part. It just, it shuddered him just how big this case might be if Seungwoo decided they need help.

“Let’s see if he really is that good or not, we need to create the team or task force soon anyway,” Sejin commented finally, he rested his head on the armchair, knocking his pencil on the cover of his notebook as he looked at the sunflower painting on Byungchan’s wall.

“Yeah, Wooseok also told me to deliver a message to you not to worry, by the way... He said he knew this guy and we can trust his capability.”

Sejin didn’t answer anymore. He was too busy thinking about the case and potential partner in work –or rival?—so he just hummed to give a signal to Byungchan that he listened to what he said. Not to worry, right, Wooseok has said.

Sejin unconsciously started waiting for tomorrow to come.

*

Precinct Busan 96 had been busy from early in the morning. Detective Kookheon and Yuvin had just brought in their main suspect of the illegal drug distribution business they have been tracing for a while, and the stubborn man nearly run away making chaos in the office. Now Eunbi was interrogating him in the secluded room trying to find the highest boss of this illegal chain. 

Seungyoun pat Sejin’s shoulder who had just brought a dark coffee from the pantry to a table behind their room, causing Sejin to flinch for the sudden contact. Among his friends, Seungyoun likes skinship with all of his friends and coworkers so much that he keeps forgetting Sejin’s rule. “You okay? It’s rare for you to drink dark coffee.”

Sejin showed a bitter smile, laughing at himself mostly because he couldn’t steal some time to sleep, trying to pull any possibility he could put down on his note. Feeling a little more ambitious than usual as if he was running out of time and there was a new deadline attached on his forehead or something.

“Yeah, I stupidly barely took time to sleep.”

“Woa, you calling yourself stupid is also new.” Seungyoun now pulled Sejin to sit down on the nearest chair. “It’s still 30 minutes left until the meeting and briefing about our case, take a moment to rest, dude.”

Seungyoun pat Sejin’s back and walked towards the door, from behind, Sejin could see a shining silver digital clock hovering above Seungyoun’s head. Sejin has always been able to see it from the first time he met Seungyoun. It used to be a countdown before he got close to Wooseok. Sejin forgot the last time he saw it was still ticking.

The moment they genuinely held hand beyond work and casual purpose, the countdown stopped. Wooseok had the same kind of countdown apparently, except it’s hidden inside his palm, glowing in metallic black like a floating ink when Wooseok opened his hand in front of Seungyoun. None of their coworkers knew the mark because, well, unlike Seungyoun, Wooseok got on Sejin’s team for not fancying too much of skinship. It took a while until they realized the fact that they were soulmates. Thanks to Wooseok for finally showing his sign on Seungyoun and he got too excited he rubbed Wooseok palm and gripped it. Genuinely grateful to see a similar mark as him. Until they realized their countdown stopped at 00:00.

At this point, Sejin could write a full romance book to tell their story on another day had he not working as a detective, considering the fact that both Seungyoun and Wooseok talked to Sejin for advice and thus making Sejin a witness of their love life and history.

Sejin sipped his coffee and massaged his forehead slowly. He never told anyone at all, that secretly, he also had a soulmate birthmark which he discovered from a long time ago when he was still a child. His grandmother had told him to be careful and not to be too attached to the mark, something that caused his grandmother to be unable of loving any person besides her destined pair –whom unfortunately refused to be committed to her and only used her as a casual fling--, her grandmother was unable to get married because of that. So she decided to adopt Sejin’s mother, who was a little lucky to find a very loving man despite not being connected by some red string of fate. Imagine if her mother had a soulmate and it’s not his father? Sejin couldn’t bet any penny on how different their life would turn out, and he wouldn’t even be here. A soulmate concept is almost like a gamble, having destined to be together doesn’t automatically make you two fall in love passionately with each other like you two were shot with cupid’s arrow of love. Some people can learn to accept and love, but so many different circumstances in life affect the route to otherwise.

Sejin touched his left forearm without folding his sleeve, there was a mark hidden beneath. A name carved like a glowing red tattoo that can’t be removed. Sejin didn’t know anyone with that name for the 24-25 years he is living in this world, not yet. He didn’t want to ponder too much on it nor tell anyone because it would be too bothersome. Though Byungchan understood he was a little sensitive about the whole couple things due to the contrast of his parents and grandmother’s story, about the whole soulmate and red string of fate which he didn’t really approve of because it didn’t make too much sense to his logical mind. When Wooseok and Seungyoun became a living proof of a happy soulmate in his logical field of work, it kind of messed him up at times.

“Hello?” a voice cut Sejin’s trail of thought, it was deep in a low tone, a voice Sejin didn’t find similar with any of his coworker so he looked up from his ritual in stirring the dark liquid in his cup.

“Yeah, may I help you with anything?” Sejin offered, he tried to stand up but much to his surprised, he staggered a little. His tolerance has always been so low for caffeine –weird considering he could chug down champagne from the bottles immediately and felt nothing— but usually, it was not this bad? Why was he getting dizzier?

“ _No_ , may I help you with anything?” The uninvited guy echoed Sejin’s question.

“I’m fine. Just need water. But I’m fine.” Sejin smiled briefly and grabbed a glass not too far from his table, filling it with water from the water cooler.

“You are detective Sejin Lee, right?” Sejin nearly fell down and crash into the water gallon. What’s with this person’s way of saying his name, Sejin Lee? Sejin held his left arm without making it too obvious, he didn’t feel anything like burning flesh or anything though?

“Uh, are you okay?” The guy asked again, trying to get closer to Sejin to help, until Sejin raised his hand up, convincing the stranger that he was really okay.

“Ah, in case you are hesitant because I sound like a weird stranger, I am Jinhyuk. Lee Jinhyuk. The new detective in this precinct.” The guy who just introduced himself as Jinhyuk now knew better than to extend his hand for a handshake.

Jinhyuk? It’s not the name carved on his arm, so why did he feel so weak earlier? Sejin finally managed to stand properly without holding onto the table’s edge, and only realized that even standing straight like this, the guy in front of him was still way taller. He wore a plaid blue shirt that’s not buttoned to the top and he didn’t wear a tie. How could captain Han let this happen? The captain usually was so strict about proper uniform and neat paperwork and look. Not a very good first impression for Sejin.

“Yeah, I am Sejin Lee,” Sejin said at last. He felt a little better and able to get himself together after the guy mentioned his name. Was it really because of stranger things? Or was his caffeine wear off slightly after he drank water?

“Yeah, Detective Sejin. I was told by the captain to call you since I was just from his room earlier. Seungyoun and Wooseok told me you are here.”

“We are about to meet in the briefing room anyway, no?” Sejin resisted the urge to ask why Jinhyuk didn’t even bother to address Wooseok and Seungyoun with the detective in front of their name. He remembered what Byungchan said about Wooseok knowing this Jinhyuk guy well, but Seungyoun too?

“He just got a call and... ah, you better ask him by yourself. The briefing might be postponed in a bit.”

Sejin squinted his eyes incredulously, wondering why would captain ask to meet him. But he eventually walked outside, leaving Jinhyuk in the coffee break room alone.

*

This was totally not what Sejin imagined one hour ago. Being in the same car with someone he just met though technically they were coworker now.

“Another person is found dead just now,” Seungwoo informed as soon as Sejin stepped inside the room. He still held his phone on his right hand, above his neck. This time it happened in less than 24 hours? The murderer seemed to be getting more in a rush.

“Wooseok and Seungyoun needed to check the previous crime scene to make sure of a certain thing and interviewed some people related to the victim to check their alibis. You, Sejin, I need you to be the team leader of this force, we will start the briefing for the new force and talked about all shreds of evidence of the three cases as soon as you are back from the latest crime scene.”

“Roger that, capt!” Sejin was quick on that, he feared that they were in for a game created by the criminal. Who will finish their mission first? A job of killing their murder list, or the detectives to prevent more murders from happening and put a stop on it.

“I have told Jinhyuk that he will be part of your team, you can learn from each other. He can be helpful. Like you, he got the most arrest when he worked in 99 last year.”

Sejin nearly snorted. But he managed to just nodded. Sejin likes talented and skilled people who could be helpful, it’s just, he hadn’t seen how this person works yet everyone he knew had already flaunted his quality to him. Not to mention the said person hadn’t quite met a good impression for Sejin.

They stopped their car in an abandoned building before entering the gate of a highway. The forensic team was still close behind them from the last time they contacted their team, Sejin walked past the silver car that’s parked next to the asphalt. He lunged his head inside the window, adjusting his white gloves until he heard Jinhyuk right behind his ear.

“We can deal with this later. Check the victim first.” Jinhyuk walked in front of Sejin, switching their previous position and while he didn’t like it, Sejin followed him inside the wide door as big as a jeep to go in. ‘The medical and forensic team were about to arrive?’ Sejin thought to himself but didn’t say anything.

⚠️⚠️⚠️

Jinhyuk checked the victim’s neck and found a little strangling mark, though it seemed to come from a necklace on his neck. “This doesn’t belong to him.” Jinhyuk put the necklace inside a plastic bag for evidence, it’s not the murder weapon, but counted as an attempt to hurt the victim through strangling. The necklace was of white gold, a letter H was carved on its pendant. Jinhyuk read the victim’s name out loud and no single letter H could be found on his name.  
Sejin lifted the cover of this male’s half lower part of the body, it was bloody like the previous cases, there were no clothes to cover it and Sejin silently held his urge to curse. The pattern was messy if this was to be done by the same person. But the consistency of killing middle-aged men and cut their vital part was showing a message of their rage, could be revenge, could be an obsession, or some sick twisted purpose only the evils knew. The bruises of struggles could be found on his arms and ankles. 

Sejin and Jinhyuk looked at each other. 

“This person might not know who the killer is.” They said in unison, which prompted Sejin to stand up first. 

“All the data on his phone had been deleted, reset to factory, but we may be able to retrieve it by checking his cloud and send the phone to the IT team.” Jinhyuk still sat down, looking for more pieces of evidence except for the male’s identity card.

“I was wondering if the three of them attended the same club which gave membership card since, from the previous cases, their body shows a high level of alcohol consumption in a short span of time.”

Sejin turned his head to Jinhyuk who hadn’t moved from his position next to the corpse’s head, “No cards were found from the previous cases.”  
Sejin walked over below the victim’s barefoot and borrowed a camera from the polices who were arrived before them, drawing the murder line and made sure everything remained in their place. “Have we found his shoes and pants?”

The subordinate shook his head, “We can’t find his shoes and pants, but his belt is right here. We found it next to that side door.”

Jinhyuk stood up and gave the plastic bag of evidence to be gathered, “We need to go check that car right now. I found a key inside his mouth, he tried to swallow it and the murderer didn’t seem to notice considering it was still there, attached between his tongue and palate.”

⚠️⚠️⚠️

Now Sejin started to wonder if Captain Han told Jinhyuk the same thing as him, that he was chosen as the captain of this force, but Sejin decided it’s unwise to ponder around it in this timing. He followed Jinhyuk’s steps to the outside, a car he was about to check earlier as soon as he arrived at the scene.

Sejin took enough distance between himself and Jinhyuk when they were rummaging inside the car, finding more clues they could find as a new lead. It’s been 15 minutes there were inside. Sejin had found one paper of emergency numbers inside the dashboard, one empty bottle of wine with dried blood on the bottle’s lips, and an old photo of graduation’s picture that’s blurred all over the paper. Sejin smelled it and deduced someone poured an unnecessary amount of alcohol on it and attempted to burn it from the corner.

Jinhyuk found one pair of socks below the passenger’s seat and managed to throw three flirts attempts to Sejin. Minus 1, no proper uniform, minus two, doesn’t know how to wait for a lead, minus three, unnecessary flirting attempts and joke around in serious situation.

“You looked too pale since before we came here, I was just trying to lighten up the mood.”

“Yeah? Thanks, I guess.” Sejin answered blindly. He tried to check the brake in the driver’s seat, while Jinhyuk was behind, rummaging under the seat to find something. He kneeled at the cushion and looked down above the car's trunk.

“You don’t seem to like working with me that much.”

“Seriously, now?” 

“Well,” Jinhyuk shrugged his shoulders, now he had turned on his flashlight from the phone to give light under every part of the car’s floor.

“Where did you take that conclusion? You are not used to someone not praising you on the spot like how everyone did?” Sejin straightforwardly blurted, causing Jinhyuk to chortle.

“You sound pissed, how many people have praised me in front of you?” Jinhyuk genuinely asked, but Sejin just snorted and decided not to take the bait of telling him how good his reputation is in front of his coworkers.

“I heard many good things about you too, you know,” Jinhyuk muttered.

Sejin turned his head to the backseat now, didn’t expect to hear what he heard just now. He could see Jinhyuk’s back, crouching down trying to reach whatever it was under. He looked hassled due to his long legs being cramped inside the low-level car. Sejin waited until Jinhyuk turned back, he raised a box proudly on his right hand until...

“Aw.”

“Jinhyuk, seriously you are too tall.” Sejin extended his hand behind the driver’s seat, helping Jinhyuk who just hit his head over the ceiling, retrieving the black iron box on Jinhyuk’s hand so he could rub his own head. 

“Me being tall is a sin too now?” Jinhyuk still teased Sejin, but he showed a key he retrieved inside earlier to Sejin, which the later quickly understood what was it for.

“Did you predict that there would be this locked secret box somewhere so you told me to come to look at the victim first?” Sejin couldn’t help but wonder, usually, he would also come straight to the victim, but he sensed the way this car was positioned when they first arrived was too suspicious. Hence he tried to look at it first. The victim parked his car facing an abandoned building instead of sideways --meaning he was not attacked in the middle of his way home, as the previous cases--, but the victim indeed planned to come inside. Sejin wondered if there was an appointment beforehand albeit not knowing who the murderer was. Now Jinhyuk tried to match the key to the box in Sejin’s hand, they both were facing each other and separated by a driver’s seat, Sejin had to kneel on the seat to match Jinhyuk’s height.

“The victim called someone to meet in this building, although due to the bruises we found, he might not know who it was, or the culprit might put on a mask. But for real, the reason why this guy was killed so quickly, in less than 24 hours and included several miscalculations like how the murderer had to use their own necklace, leaving more clue, is because this one might be an impromptu murder.”

If Sejin was impressed by Jinhyuk's quick way of thinking, he sure didn’t show it. Sejin quickly lifted the box’s lid and looked inside, several photos and documents were hidden beneath a sky blue silk clothes. Sejin looked at Jinhyuk intensely.

“Jinhyuk, perhaps you were right. This box might be the reason why the victim called the suspect. He tried to stop the chain, or save himself. But he was guilty of something so he couldn’t report and ask our help... Rather, he tried to solve this series of riddle blackmails alone.” Sejin raised the papers in his hand.

“Right, let's move to our car and head to the office, we need to match data we find with Wooseok’s side and trace the suspect.”

*

“You still need to tell me about two things, in case you forget.” Sejin started a conversation when Jinhyuk raced towards their office.

“What? That you are beautiful with glasses? I haven't told you that?” Sejin rolled his eyes, as an Aries he knew better than to trust a Gemini's mouth and take their flirting seriously, yes, he got this information from Byungchan please don't follow his way. This has been the fifth attempt of Jinhyuk throwing casual flirty remarks to Sejin, he wondered if Jinhyuk was like this to everyone? Not that he cared or anything.

“About what you heard about me.” 

Jinhyuk's laughter erupted loudly, “What about I tell you later if you get more arrests than me until next Halloween?”

Sejin held his seatbelt and slightly turned his body to face Jinhyuk from the passenger's seat. Did this person just challenge him?

“Spoiler, I know from Wooseok you are the most reliable in arresting most people in precinct 96.” 

“What's the bet?” 

“Go on a date with me.”

“Dude?” Sejin frowned, couldn't believe what he just heard.

“You have been so strict with rules and works and barely got time to find yourself a date for the past year, right?”

Now Sejin swear he would smack his friend who spilled this tea to Jinhyuk, was it Seungyoun or Wooseok since they knew each other? They just met and Jinhyuk acted like he knew a lot about him. 

“Consider yourself checking one to-do list of finding a mate to attend a Halloween party this year, way months earlier than D-day.” Jinhyuk grinned, showing his bright white teeth, the sun reflected its shining light on his cheeks and Sejin nearly slapped himself.

“Then I want your sports car.”

Jinhyuk nearly pulled his brake and the car swayed a little, “What?”

Sejin lifted one of his eyebrows and tilted his head, showcasing his innocent look (which god forbid anyone would see this because he never pulled this stunt except in front of his mother back in the day when he wanted something, or when he needed a favor from Wooseok once in a blue moon). “I want this car for the bet. It's way faster and I need it to catch more criminals. I can't?”

Jinhyuk cursed under his breath. Sejin was not someone to play around with.

“Okay, you can get this car.”

“But....” Jinhyuk paused, “Only if you win and get more arrest than me. If I win, I got the date, and you must follow my rules, no controlling detective Sejin for the day.”

Sejin grunted, “Sure, deal.” He said before facing the front view again, resting his back on the seat, as they were getting closer to the office. Silence filled the car and only smooth machine noise could be heard for a while after they started their bet. Sejin held a bag of evidence on his lap.  
They were just arriving in Busan 96 parking lot when Jinhyuk turned to Sejin and said something which caused Sejin to freeze for nearly three seconds.

“About the victim, I just wanted to make sure his state. If we arrived earlier and he could still be saved, then we could call the hospital. Since the report came from a common citizen, the first thing they know is to call police, not hospital since it would require money if they ended up asking the witness to handle the administration. That's not how it works, but that's what _people_ thought how it works. So it's under our responsibility too to check if they are still alive somehow? Our responsibility to call an ambulance.”

Sejin listened attentively to what Jinhyuk explained. Even until Jinhyuk had come out of the driving seat, Sejin was still thinking of what Jinhyuk said.

Perhaps this person was not so bad.

*

__Perhaps, this person was not all that good._

First exhibit. Sejin screamed at himself when he got home the day after he met Jinhyuk. The name on his arm had changed, it's no longer a name carved like a glowing red tattoo, but it looked like a scar of removed tattoo instead. What did that mean? Did he just lose his soulmate? And was it triggered by Jinhyuk's arriving in his life? 

The second exhibit, today. Sejin nearly screamed and yelled at Jinhyuk when he left all the paperwork all Sejin, by mischievously taking a stakeout job when the due time for this paperwork of their serial murder case not too long ago was getting closer. 

They have solved the case together, along with Wooseok and Seungyoun, and able to stop the chain at fifth murders from the original revenge plan of killing 15 people, found a lead to the murderer five days after Jinhyuk found the little box and captured them.

From their time of working together, Sejin found out Jinhyuk likes action and spy movies a lot and he enjoys the thrill of chasing and capturing culprits. But the paperwork? Ha. Don't expect anything from him. Sejin stretched his arms on the bathroom behind the pantry, he finally finished the damn paperwork and prepared to go home. Some colleagues like Eunbi, Yuvin, and Byungchan were still at the office since they had more paperwork to do too.

Sejin rubbed his left forearm. He still hadn't figured out what happened, the name didn't appear again on his arm ever since that day. Did Jinhyuk really exile his soulmate's existence or were they not related?

Sejin stretched his arms again and walked outside the coffee break room. He better prepared for another case he had. This month’s count was still tied, both Jinhyuk and Sejin arrested 10 people so far. Sejin really needed to win this.

*

Sejin needed to win this for many reasons. One, he wanted Jinhyuk's car.

Second, he didn't, doesn't, and wouldn't want to do _this_.

Sejin adjusted his glasses and looked at his childlike costume once again, sure this character which Jinhyuk chose for him is a detective, but... detective Conan, really? Sejin shook his head at the short dark blue pants and suits he wore, a red bow attached on his neck, in which Jinhyuk had installed a real microphone beneath the bow. The dedication he had...

Jinhyuk came out from his car (which failed to fall under Sejin's grasp, _sigh_ ), with a white top hat with a blue ribbon band that made him even taller than he already is. Jinhyuk adjusted his monocle that covered his right eye, which had a dangling green charm with a white clover imprinted on it. Jinhyuk's outfit consists of a white suit jacket on top of a blue shirt with a red tie and white dress slacks. He turned around and stood next to Sejin, which looked even tinier with his costume now.

_Why must Sejin lost by two arrests only, it was so close, so close..._

Now here he was.

Jinhyuk grinned so wide as if he could smile from his left to right ear, he enjoyed the night when he had Sejin willingly cling onto his left arm. Sejin still hated skinship and Jinhyuk respected that usually, but this time, when the bet was at hand and Sejin insisted he is a man of his words, Sejin didn't mind to attach himself to a guy who had been his rival for the past 7 months.

For a bet.

Sejin convinced himself it was just for a bet.

Ignoring the fact that every time Jinhyuk mentioned his full name, Sejin Lee, he felt like his heart was about to leap.

*

Sejin still feels the way his heart wants to leap every time Jinhyuk puts an emphasis on his name, Sejin Lee, to this day.

Sejin still wants to run away and slaps his cheeks secretly sometimes when he wakes up and finds Jinhyuk, his coworker, is sleeping soundly on his side. On his bed. On their house.

Sejin still can't believe how this is the same man he married two months ago after dating for one year. Sejin can't believe this is the same man he used to find irritating back in the day. But above all of those.

Sejin feels contented. 

This is the life he wanted. The kind of loving life like how their parents love each other without a red string of fate playing their lines.

Sejin almost forgot he ever had another name other than ‘Jinhyuk’ carved on his left forearm, which magically got removed the moment Jinhyuk appeared in his life. The scar was still visible though. But now that he married Jinhyuk, Sejin noticed how slowly the scar was healed. Slowly changed into a little sunflower tattoo instead.

Sunflower tattoo which Sejin wouldn't notice if it's not for Jinhyuk.

They were having a workcation that day, staking out in a hotel near a building that was used by a group of robbers to camp. Wooseok and Seungyoun in the next room took a turn to watch while Sejin was resting on Jinhyuk's arm as a pillow. They didn't do anything other than talking, throwing a random riddle to each other to solve.

Until Jinhyuk gently pats Sejin's left arm and got his eyes widened.

“Wait, you got a new tattoo? It's a sunflower.”

“What?”

They both woke up and looked at Sejin's left forearm. Jinhyuk traced the freshly carved sunflower slowly. “This looks beautiful, like you.”

Sejin didn't say anything, wondering whether this is finally a good time to tell Jinhyuk about his soulmate thing. Why did this mark still change?

“Jinhyuk...” Sejin stared at Jinhyuk and touched his partner’s hand, sometimes still can't believe at how much he changed to a certain person only.

“Do you believe in a soulmate?” he started in a low voice, causing Jinhyuk to just smile and pulled the shorter guy into his embrace, always fits so well on his lap. Jinhyuk rested his head on Sejin's head from behind and planted a kiss on it.

“Yeah, it's you.”

“Me?”

Jinhyuk laughed softly and wrapped his arms around Sejin, linking it to Sejin's fingers, playing with it.

“I don't care much actually, but I thought you know already that I had a sun tattoo on my right back?”

“I thought it was just a regular tattoo...”

“It appeared the night after I met you.”

“What? Really? Why didn't you tell me?”

“You sounded like you hate soulmate stuff, so I didn't want you to think I made a move on you because I believe you are my soulmate... because trust me, that's never my sole reason.”

Sejin turned himself hesitantly, trying to look at Jinhyuk on the eyes to admit something.

“But I had another man's name on my arm... before I met you. I thought it was not you.”

Jinhyuk's forehead was creased, “Huh? Who was it? I never knew a case where a soulmate could change, though.”

“The name was... Sungjun.”

Jinhyuk, who was nearly frowning, ended up blurting out a peal of laughter so loud upon hearing the name. God, why didn't Sejin tell him? Sejin looked at him blankly, confused. But Jinhyuk still couldn’t stop laughing.

“Sejin Lee, listen.” Jinhyuk held Sejin's shoulders, “It was my old name.”

“Jinhyuk, don't joke around.”

“SBo, really... it was my name before I legally changed my name like.. a year before I met you. I changed my name due to family reasons.”

Sejin's jaw dropped, couldn't believe this kind of story could actually happen to him, someone who was always hesitant on what to think about soulmate and walked around eggshells for it. So, it disappeared after Jinhyuk introduced his name as Jinhyuk to Sejin?

“Dude.” Sejin finally managed to utter one word. He was at loss for words.

“Yeah, I love you too, Dude.” Jinhyuk pulled Sejin inside his embrace again, letting Sejin hide his smile against his chest. He knew his Sejin would be embarrassed to show it obviously.

Jinhyuk kissed Sejin's forehead and about to peck his nose when his phone buzzed aggressively.

It's Wooseok.

_Dumbass tone your laugh down_  
_Do you forget we are on a stakeout?????_  
_This is not a honeymoon nor workcation THIS IS A STAKEOUT???_  
_THIS IS A STAKEOUT_

Jinhyuk nearly laughed out loud again reading Wooseok's messages.

But, he managed to restrain himself, as he kissed his Sejin Lee goodnight.

FIN.

**Author's Note:**

> Disclaimer: This story is purely fictional, the way the precinct works in this alternative universe is heavily inspired by Brooklyn 99 (SejinHyuk's bet is also adapting Jake and Amy's bet) with much modification, the characters in this AU are completely developed by the writer, and not related to the real idol whose name and visualization are borrowed. Please refrain from hating them due to this fictional work.
> 
> The given prompt: rivals to lovers within soulmate AU with a happy ending. I decided to tweak a bit by using Brooklyn 99 setting because I want to see how Sejinhyuk would look like if they were to have Jake-Amy's rivalry.
> 
> As I write for this work... I realized I want to slowly build the universe from the first time they met and I am thinking that a one-shot wouldn't be enough to convey the whole story I had in my head. So, I decided to omit the solution of the criminal case I presented in the beginning, I have the whole details to the crime ready but it is to be explored later once I expand the universe, I want to explore more about their dynamic in this kind of setting.
> 
> I may remake this either in multi chapters fic or social media AU setting (let's see!)
> 
> Comments are greatly appreciated since I need input on what to fix and what people think of this universe before I expand it. Thank you!


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